The 2nd-generation mobile communication refers to transmission/reception voice data in a digital manner, which includes CDMA, GSM, and the like. As an advanced level of GSM, GPRS has been proposed to provide a packet switched data service based on the GSM system.
The 3rd-generation mobile communication refers to a scheme for transmitting and receiving image and data. A Third Generation Partnership Project (3GPP) has developed a mobile communication system (IMT-2000) and adopts WCDMA as a radio access technology (RAT). A scheme combining the IMT-2000 technology and the RAT, e.g., the WCDMA, is called universal mobile telecommunication system (UMTS). A UTRAN stands for a UMTS terrestrial radio access network.
The 3rd-generation mobile communication is evolving into 4th-generation mobile communication.
As the 4th-generation mobile communication technology, a long-term evolution network (LTE) technique under standardization by 3GPP and an IEEE 802.16 technique under standardization by IEEE have been proposed. The LTE uses a term of an evolved-UTRAN (E-UTRAN).
For the 4th-generation mobile communication technology, an orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) have been introduced. OFDM uses orthogonality between inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT). A transmitter performs IFFT on data and transmits the same. A receiver performs FFT on a reception signal to restore the original data. The transmitter uses IFFT to combine a plurality of sub-carriers, and the receiver uses corresponding FFT to separate the plurality of sub-carriers.
Meanwhile, in the 3rd or 4th-generation mobile communication system, attempts for increasing a cell capacity continues to support high capacity services such as multimedia contents, streaming, and the like, and bi-directional services.
An approach of using a high frequency band and reducing a cell radius has been proposed to increase the cell capacity. The application of a cell with a relatively small cell radius such as a pico cell or the like can use a higher band than the frequency band used in the existing cellular system, having an advantage that more information can be transmitted, but also there is shortcomings in that more base stations should be installed in the same area, incurring more costs.
As one of approaches for increasing the cell capacity by using smaller cells, a femto cell has been proposed.
A femto cell refers to providing a small radio environment by installing a very small base station with low power consumption at homes or offices. The femto cell can enhance quality of service (QoS) by improving an indoor service available area and increasing capacity, and is expected to completely settle the next generation mobile communication system by providing data services.
In this respect, however, the reduction in the cell radius may lead to dense base stations in a particular area, and because of unnecessary overlap installations of base stations, interference is generated, radio resources are ineffectively used, and a system performance is degraded.
In particular, in the femto cell cellular system, a femto base station (femto BS) can be arbitrarily installed by a user, and such installation of femto BSs possibly causes an overcrowded femto BSs.
In the related art as described above, an installation position of an femto BS is selected by each user, and the femto BS has a smaller coverage compared with a macro-base station and provides a service to a smaller number of determined users.
Thus, the location distribution of users much affect the interference relationship between femto BSs. Unnecessary overlap installations and overcrowded installations may be caused, and in a residual area or offices are crowded, the distance between installed femto base stations is narrow.